The Earth Federation is on the brink of war with the rival Draconian Empire. When the Doctor and Jo arrive, they discover someone is trying to inflame the tensions between the two space powers. They quickly learn that the culprit is the Master, but before they can deal with him, the evil Time Lord has them framed as Draconian spies. Worse still, the Master is not working alone...

As Season Nine was being recorded in 1972, producer Barry Letts and script editor Terrance Dicks were formulating suitably celebratory plans for Doctor Who's tenth year of broadcast. The cornerstone of the season would be an adventure bringing back past Doctors William Hartnell and Patrick Troughton -- latterly titled The Three Doctors -- but Letts also wanted to challenge the series record for longest story, held by Season Three's twelve-part The Daleks' Master Plan.

However, that story's director, Douglas Camfield, warned Letts about the significant difficulties such a lengthy production had presented, while Dicks was concerned about retaining an audience through almost three months' worth of a single story. Instead, it was decided to devise two connected six-part stories, each featuring one of the Doctor's two most popular enemies: first the Master, then the Daleks. The writer chosen for the first serial was Malcolm Hulke, whose last contribution had been The Sea Devils for Season Nine.

Letts and Dicks presented Hulke with several requirements for his storyline, which was commissioned as “Frontiers In Space” on April 14th, 1972. First, for budgetary reasons, the Master could only feature in the last four of its six episodes. Also, the evil Time Lord should be teamed with the Ogrons, monsters introduced in Day Of The Daleks the previous year: these had been a popular creation, and would also help link into the subsequent Dalek serial, Planet Of The Daleks. Finally, the production team wanted to take advantage of various spaceship models which the BBC had recently acquired from Gerry Anderson and Century 21, creators of a variety of marionette science-fiction programmes. For his part, Hulke wanted to develop an intergalactic parallel with the ongoing Cold War between the United States and the Union of Soviet Socialist Republics.

Hulke was commissioned to write his six scripts on May 4th, under the slightly amended title of Frontier In Space (though the pluralised form would continue to be used occasionally in the lead-up to production). The original rival Hulke had devised for the Earth Federation was the Andromedan Empire; this became the Draconian Empire. The author had intended their culture to be like the post-Napoleonic Hapsburgs, although their eventual execution was more akin to a Japanese shogunate. The human president changed gender to female during the writing process, while the inmate Doughty was rechristened Patel. In his scripts, Hulke gave the prison governor the name Stevens.

Although Frontier In Space was scheduled to be the third broadcast story of the season -- after The Three Doctors and Carnival Of Monsters -- it was actually recorded first in the tenth production block. This was because Troughton's schedule forced a delay in taping the multi-Doctor adventure, while Carnival Of Monsters had already been completed at the end of the preceding block. As such, Frontier In Space became Serial QQQ. Its director was Paul Bernard, who had just worked on The Time Monster at the end of the previous season.

Frontier In Space required considerable model filming, which occurred on August 14th, 18th and 22nd at Bray Studios. Four days of location filming then began on September 10th at the Hayward Gallery in Lambeth, London; this served as the Earth prison. The next two days were spent at Beachfields Quarry in Redhill, Surrey, for material on the Ogron planet. Finally, the 13th took cast and crew to Fitzroy Park in Highgate, London, which was the exterior of the Draconian embassy. The spacewalk scenes were then filmed at the Ealing Television Film Studios on September 14th.

Episodes one and two were recorded on Monday, October 2nd and Tuesday, October 3rd. The third and fourth installments followed exactly two weeks later, on the 16th and 17th, during which Delgado joined the production. Although the final studio block was originally scheduled for another Monday and Tuesday -- the 30th and 31st -- the recording of part five was postponed until Wednesday, November 1st (although the cliffhanger was taped alongside episode six the day before). These last two installments were recorded in BBC Television Centre Studio 3, while the rest of the serial had been enacted in TC4.

Unfortunately, Letts was by now extremely unhappy with the Ogron Eater, feeling it looked like little more than an unthreatening formless blob, rather than the scripted gargantuan lizard. To make matters worse, the monster was a key element of Hulke's climax. As written, the end of part six would see the Ogrons recapturing Williams and the Draconian prince, and the Master then confronting the Doctor and Jo. The Doctor activates the hypnosound machine, appearing to the Ogrons as the Eater. The Master shoots at him, only to have a panicking Ogron felled by the weapon instead. The Master escapes, pursued by Williams and the prince, while the Doctor and Jo set off in the TARDIS to pursue the Daleks. Letts decided to minimise the use of the Eater as much as possible, and so new material -- featuring only the Doctor and Jo -- was written which could be edited into the climax. This was recorded during the first studio day for Planet Of The Daleks on January 22nd, 1973, in TC4.

Like Carnival Of Monsters, Frontier In Space was originally prepared with the new “Delaware” arrangement of the theme music played over the credits. After its poor reception by BBC brass, however, this was replaced, although an early edit of episode five survives with the Delaware theme intact.

As it transpired, Frontier In Space was Paul Bernard's final work on Doctor Who. He would go on to direct episodes of programmes such as The Tomorrow People and EastEnders. More recently, Bernard has concentrated on a successful career in art.

During production on Frontier In Space, Roger Delgado had informed Letts that he wished to make just one more appearance as the Master. Many producers believed that he was still working full-time on Doctor Who (as had been the case during Season Eight) and so were not considering him for other work, even though Delgado was now featuring in just one or two Doctor Who stories per season. It was agreed that Delgado would therefore appear in a single adventure during Season Eleven in which the Master would sacrifice his life to save the Doctor.

Letts began work on Delgado's swansong, “The Final Test”, with Robert Sloman in early 1973. Unfortunately, this serial was not to make it into production. On June 18th, 1973, Delgado flew to Turkey to film material for a French comedy called Bell Of Tibet. His flight was late arriving, inciting his chauffeur to drive too quickly along treacherous mountain roads to the programme's location in Nevsehir. Tragically, the car left the road and plummeted into a ravine, killing Delgado and a Turkish technician, and bringing a premature end to both a beloved Doctor Who character, and indeed a beloved member of the acting profession.

• Doctor Who: The Handbook: The Third Doctor by David J Howe and Stephen James Walker (1996), Virgin Publishing, ISBN 0 426 20486 7.
• Doctor Who: The Seventies by David J Howe, Mark Stammers and Stephen James Walker (1994), Virgin Publishing, ISBN 1 85227 444 1.
• Doctor Who Magazine #201, 7th July 1993, “Archive: Frontier In Space” by Andrew Pixley, Marvel Comics UK Ltd.
• Doctor Who Magazine Special Edition #2, 5th September 2002, “Saturday Night's Alright For Fighting” by Andrew Pixley, Panini Publishing Ltd.